Method and tool for optimizing fuel/electrical energy storage allocation for hybrid-electric aircraft

ABSTRACT

A hybrid interchangeable battery evaluation tool (HIBET) is provided. HIBET determines an amount of electrical energy and an amount of jet fuel necessary for a hybrid electric aircraft to complete a flight based on a range of the flight, a payload of the hybrid electric aircraft, an indication of a battery mass limitation of the hybrid electric aircraft, and an optimization of an energy split between the electrical energy and the jet fuel. HIBET causes an indication of the amount of electrical energy to be displayed in a graphical user interface and/or to be otherwise outputted.

TECHNICAL FIELD

This disclosure relates to aircraft and, in particular, tohybrid-electric aircraft.

BACKGROUND

A hybrid-electric aircraft may include a propulsion system thatcomprises one or more gas turbine engines and an electrical systemconfigured to provide propulsion or provide electrical energy used inpropulsion of the hybrid-electric aircraft. The gas turbine engine(s)burn fuel for propulsion. The electrical system may include one or moreelectric motors and one or more batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments may be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale. Moreover, in the figures, like-referenced numeralsdesignate corresponding parts throughout the different views.

FIG. 1 illustrates an overall modelling framework for HIBET, which showssome inputs and outputs of HIBET;

FIG. 2 illustrates three high-level systems that benefit from HIBET;

FIG. 3 illustrates examples of HIBET input assumptions on annualprojections to a specified future date;

FIG. 4 illustrates physical constraints governing the split betweenbattery and fuel and an example of an energy/cost optimization of thesplit.;

FIG. 5 illustrates a weight comparison of fuel energy and electricalenergy per applied MJ of energy at two different times;

FIG. 6 illustrates a summary of a design envelope for aircraftpropulsion;

FIG. 7 illustrates an example of projected battery costs;

FIG. 8A illustrates energy calculation parameters where Pm<=Pcr;

FIG. 8B illustrates energy calculation parameters where Pm>Pcr;

FIGS. 9A and 9B illustrates a % Energy Limit calculation for thetake-off flight segment under the condition where Pm<=Pcr;

FIGS. 10A and 10B illustrates a % Energy Limit calculation for thetake-off flight segment under the condition where Pm>Pcr;

FIGS. 11A and 11B illustrates a % Energy Limit calculation for thecruise flight segment under the condition where Pm<=Pcr;

FIGS. 12A and 12B illustrates a % Energy Limit calculation for thecruise flight segment under the condition where Pm>Pcr;

FIG. 13A shows an example distribution of range and number of passengersfor an Airbus A320 family;

FIG. 13B shows an example distribution of range and number of passengersfor a Boeing B737 family;

FIG. 14A illustrates a graph generated by HIBET displaying thecorresponding battery masses and energy/fuel work ratios;

FIG. 14B illustrates a graph generated by HIBET displaying thecorresponding relative costs and relative emissions;

FIGS. 15A and 15B illustrate the effect of doubling the motor powerratings per engine;

FIGS. 16A and 16B illustrate the effects of increasing an aspect of thestructure/volumertic limit of the aircraft;

FIGS. 17A and 17B illustrate the effects of increasing the MTOW of theaircraft;

FIGS. 18A and 18B illustrate the effects of changing the value limitconstraint;

FIG. 19 is an example of a graphical user interface generated by HIBETthrough which aircraft data may be entered;

FIG. 20 illustrates an example of a fuel mass map;

FIG. 21 illustrates an example table of mission distributions for theaircraft;

FIG. 22 illustrates an example of a graphical user interface to receiveeconomic and technological variables pertaining to energy and hybridcomponent cost;

FIG. 23 illustrates an example of a graphical user interface configuredto receive additional technological factors and general characteristicsof a conventional turbine engine;

FIG. 24 shows an example of a graphical user interface configured toreceive details of the aircraft hybrid-electric system;

FIG. 25 illustrates an example of a graphical user interface showing atable of economic and technological variables that pertain to energy andhybrid system component costs;

FIG. 26 illustrates an example graphical user interface displayingenergy requirement calculations of the aircraft;

FIG. 27 illustrates an example of a graphical user interface displayingenergy cost calculation of conventional turbine-powered aircraft basedon the output table of economic and technological variables;

FIG. 28 illustrates a graphical user interface displaying the requiredenergy calculation during each stage of the mission for ahybrid-electric aircraft;

FIG. 29 illustrates an example of a graphical user interface displayingmaximum energy during each stage of the mission for a hybrid-electricaircraft;

FIG. 30 illustrates an example of a graphical user interface thatdisplays an indication 3002 of the amount of battery to install on thehybrid-electric aircraft for each interval of a mission range;

FIG. 31 shows the total energy and mass defined for the hybrid-electricaircraft and the MTOW Limit;

FIG. 32 illustrates an example of a graphical user interface displayingthe emissions and the costs associated with the conventional gas-turbineversion of the aircraft;

FIG. 33 illustrates an example of a graphical user interface displayingthe emissions and the costs associated with the hybrid-electric versionof the aircraft;

FIG. 34 illustrates an example of a graphical user interface displayinga table for normalizing the distribution of flights of the definedairframe with the defined payload;

FIG. 35 illustrates an example of a graphical user interface displayingaverage per-flight fuel cost and emissions savings of the definedaircraft and payload;

FIG. 36 illustrates an example of a graphical user interface displayingfleet-averaged results of aircraft hybridization;

FIG. 37 illustrates an example of a graphical user interface displayingthe total annual fleet-wide savings due to hybridizing the fleet;

FIG. 38 illustrates an example of a computing device or system thatincludes HIBET; and

FIG. 39 illustrates a flow diagram of an example of steps performed byHIBET.

DETAILED DESCRIPTION

A hybrid interchangeable battery evaluation tool (HIBET) is describedherein. HIBET generates information related to sizing batteries for ahybrid-electric aircraft. Alternatively or in addition, HIBET identifiesand outputs the value of hybridization of the aircraft.

As mentioned above, the hybrid-electric aircraft may include apropulsion system that comprises one or more gas turbine engines and anelectrical system configured to provide propulsion or provide electricalenergy used in propulsion of the hybrid-electric aircraft. The gasturbine engine(s) burn fuel for propulsion. The electrical system mayinclude one or more electric motors and one or more batteries. Thebattery and/or batteries may be interchangeable, which means that thebattery and/or batteries may be swapped in or out of the hybrid-electricaircraft. The number and/or size of the interchangeablebattery/batteries may vary. Accordingly, determining an optimal numberand/or size for a flight having a specified range and a specifiedpayload is useful.

Based on selected airframe parameters and other variables, HIBEToptimizes an energy split between battery and fuel for flight missionsranging up to, for example, 3500 nm (nautical miles). HIBET evaluatesthe energy at a high level using a first principles evaluation and assuch may not necessarily model the performance and weight of the gasturbine, the electrical distribution system, the thermal managementsystem, or the physics of the electrical energy storage system. The toolmay not necessarily consider the impact of changes in the propulsionsystem on the weight and drag of the aircraft or determine the totalmission fuel and energy consumption. Such assessments may be determined,for example, using other simulation tools, such as NPSS (NumericalPropulsion System Simulation) and Pacelab ADP. FIG. 1 illustrates anoverall modelling framework for HIBET, which shows some inputs andoutputs of HIBET.

HIBET is implemented in a spreadsheet application in some of thefollowing examples. In such examples, cells of the spreadsheet areoccasionally identified for convenience. The identified cells mayinclude input variables, output values, functions, and/or fields of agraphical user interface. However, as described in more detail furtherbelow, HIBET may be implemented in any type of software. In these othertypes of software, the cells mentioned herein may instead refer tovariables, output values, functions, and/or fields of a graphical userinterface for example.

In one aspect, a non-transitory computer readable storage mediumcomprising a plurality of computer executable instructions in provided,where the computer executable instructions executable by a processor.The computer executable instructions comprise: instructions executableto receive, prior to a flight by a hybrid electric aircraft, anindication of a limitation of battery mass for the hybrid electricaircraft; instructions executable to determine, based on the indicationof the limitation of battery mass and prior to the flight, an amount ofelectrical energy and an amount of jet fuel necessary for the hybridelectric aircraft to complete the flight based on an optimization of anenergy split between the electrical energy and the jet fuel; andinstructions executable to cause an indication of the amount ofelectrical energy and the amount of jet fuel to be displayed in agraphical user interface and/or to be otherwise outputted.

In another aspect, a method is provided in which: an amount ofelectrical energy and an amount of jet fuel necessary for a hybridelectric aircraft to complete a flight is determined based on a range ofthe flight, a payload of the hybrid electric aircraft, an indication ofa battery mass limitation of the hybrid electric aircraft, and anoptimization of an energy split between the electrical energy and thejet fuel; and an indication of the amount of electrical energy is causedto be displayed in a graphical user interface and/or to be otherwiseoutputted.

In yet another aspect, a system is provided comprising an optimizedbattery works module and a graphical user interface. The optimizedbattery works module is configured to determine an amount of electricalenergy and an amount of jet fuel necessary for a hybrid electricaircraft to complete a flight based on a range of the flight, a payloadof the hybrid electric aircraft, an indication of a battery masslimitation of the hybrid electric aircraft, and an optimization of anenergy split between the electrical energy and the jet fuel. Thegraphical user interface comprises the amount of electrical energy to bedisplayed.

Introduction

FIG. 2 illustrates three high-level systems that benefit from HIBET.

System 1 includes the aircraft carrying the passengers, and morespecifically, the propulsion system of the aircraft. System 2 includesan engine manufacturer that continues to develop and/or implement enginetechnologies. System 3 includes airline operators who use the aircraft.

The hybrid interchangeable battery evaluation tool (HIBET) enables anassessment of hybridized aircrafts (system 1) operating in a definedworld (system 3). HIBET takes a range of input parameters and inputassumptions on annual projections to a specified future date, such as2040 to calculate their impact on the value to the customer, and hence,the engine manufacturer. FIG. 3 illustrates examples of HIBET inputassumptions on annual projections to a specified future date.

The HIBET utilizes fundamental energy assessments to optimize the energysplit between battery and fuel. The split between battery and fuel isgoverned by physical constraints that are defined by the aircraftarchitecture. FIG. 4 illustrates physical constraints governing thesplit between battery and fuel and an example of an energy/costoptimization of the split. Physical constraints governing the split mayinclude: Power Limit, Structural/Volumetric Limit, MTOW Limt, and ValueLimit.

Power Limit—defined by the power rating of the electrical machines.Limits the peak draw on battery energy during the flight profile. Tendsto be more restrictive at take-off when the power requirement is at itshighest.

Structural/Volumetric Limit—Structural: the maximum load bearingcapability of the fuselage, often referred to as maximum zero fuelweight (MZFW); Volumetric: the maximum allowable space for locatingenergy storage.

MTOW Limit—Maximum Take-Off Weight of the aircraft based on theaerodynamic/thrust limitations of the aircraft.

Value Limit—the cost neutral point between a conventional and ahybridized aircraft above which the cost of carrying the additionalweigh of the batteries exceeds energy cost savings from fueldisplacement.

Hybridization

Cost and weight per MJ (megajoule) of applied (thrust) energy are twokey values to assess the feasibility of hybridization at a high level. Afair comparison between a conventional and hybrid must account for theefficiency of energy extraction for useful applied work (thrust). Onesimple example approach to the determining cost is to assume that theconventional and hybridized aircraft are sufficiently similar instructure that any weight differences and other factors are judged to beinsignificant. This demonstrates that electrical energy is cheaper thanjet fuel based energy. Based on today's jet fuel and electrical energyprices, the cost per applied MJ of energy from jet fuel is approximately1.5× more than for electricity. Electricity rates are predicted toremain largely flat into the future, yet jet fuel costs may increasesignificantly, whether the result of a direct rise in oil costs and ordue to the introduction of an aviation emissions tax. Under such anexample scenario, jet fuel applied (thrust) energy may be at 5× morethan electricity in the future.

The argument for hybridization using today's technology is lessfavorable when viewed from a comparison of mass per MJ of applied(thrust) energy than it likely will be in the future. FIG. 5 illustratesa weight comparison of fuel energy and electrical energy per applied MJof energy at two different times: today and in the future usinghypothetical values. If the current state of the art batteries offersabout 200 Wh/Kg (Watt-hours per Kilogram) for example, a hybridizedaircraft would need to carry 35× more energy weight in the form of abattery per MJ of applied (thrust) energy than in the form of jet fuel.With some people estimating the projection of current lithium-iontechnologies being a theoretical maximum energy density of approximately850 Wh/Kg, this reduces to about 9× more energy weight in the form of abattery. For batteries to achieve comparable energy weight to that ofapplied (thrust) energy from jet fuel, new battery technologies may needto achieve energy densities of 7,764 Wh/Kg if all other factors, such asthe price of jet fuel, remain unchanged.

FIG. 6 illustrates a summary of a design envelope for aircraftpropulsion. The summary is defined in terms of propulsive power on thex-axis and power extraction on the y-axis. The relative power extractionand propulsive power for multiple types of electric hybrid propulsionsystems are shown. Examples of the electric hybrid propulsion systemsmay include Parallel Hybrid, Boosted Parallel Hybrid, Series/ParallelHybrid, Turbogeneration, Electrically Distributed Propulsion, PartiallyDistributed Propulsion, and Series Hybrid.

A hybrid interchangeable battery evaluation tool (HIBET) is describedherein. Based on selected airframe parameters and assumptions, HIBET mayoptimize an energy split between battery and fuel for flight missionsranging up to 3500 nm (nautical miles).

HIBET Constants

Common constants and conversions embedded in the HIBET functions areshown in Table 1.

TABLE 1 Common constants and conversions Constant/Conversion FunctionDescription Factor Mass To convert from Kg to lb, Kg multiplied byfactor 2.2 Energy To convert from MJ to Wh, MJ multiplied by factor277.778 Jet Fuel Energy Specific Energy Density of fuel 43 MJ/Kg contentJet Fuel carbon The weight of carbon produced for the combustion of 1 lbof fuel is the 3.1 production fuel mass multiplied by factor Jet Fuelweight per The weight of jet fuel in lbs is the number of gallons offuel multiplied 6.79 gallon by factor

Input Parameters

Airframe selection for the analysis determines the airframe dependentinput variables to be used. Airframe input variables are shown in Table2.

TABLE 2 Airframe Input Variables Independent input Excel variablesFunction Description column/cell Payload/Max Payload Ratio of actualpayload to maximum allowable payload Cell P3 Takeoff Power per MW ratingof take-off power per engine Cell P4 Engine Cruise Power per MW ratingcruise power per engine Cell P5 Engine Max Payload Max allowable payloadCell R7 MTOW Maximum Take-Off Weight Cell T7 Range (nm) Flight range insegments of 100 nm Column A Fuel (lb) Fuel required for conventionalairframe for a given nm - fuel Column B consumption derived from theaircraft model (APD and Mission software) converted to a regressionbased formula for range, max payload and MTOW OEW (lb) Operating EmptyWeight;, or Basic Operating Weight for the Column C conventionalaircraft; the weight of the conventional aircraft, unfueled with nopayload Payload (lb) Selected payload for the simulation - product ofthe maximum Column D payload (Cell R7 and the ratio of Payload to MaxPayload (Cell P3). Represents the weight of passengers and their baggage

Table 3 describes additional independent variables.

TABLE 3 Independent Input Variables Independent input Excel variablesFunction Description column/cell Projected Year Year selected for allregression based projection functions/formulas Cell B3 Operating ModeSelection of solving parameter. 1 = Solves for maximum displacement CellB4 of the fuel using battery regardless of cost and emissions whilingachieving mission range, 2 = Solves for minimum cost of energy, 3 =Solves for minimum jet fuel consumption, 4 = Solves for minimum totalemissions Grid Energy Cost Level of projection for energy costs, Lowthrough High (L = 1, M = 2, Cell B5 Outlook H = 3) Fuel Cost ProjectionLevel of projection for jet fuel costs, Low through High (L = 1, M = 2,Cell D3 H = 3) Nuclear Discount The discount rate, otherwise referred toas “discounted cash flow Cell D4 Rate analysis” is the effectivereduction in future projected profits when accounting for them intoday's monetary value. Nuclear is significantly more sensitive todiscount rate than coal or gas due to being capital intensive. Thediscount rate chosen to cost a nuclear power plant's capital over itslifetime is arguably the most sensitive parameter to overall costs andhence levelized cost of electricity (LOCE). At a 3% discount ratenuclear power is typically the cheapest form of energy production. At 7%it is comparable to coal, but still cheaper than gas. At 10% it iscomparable to both. % Nuclear % of dedicated carbon free energyproduction for charging batteries, Cell D5 Generation i.e. 40% nuclearwould imply 60% is still based on regional grid mix composition RegionalUS Grid Represents the US grid mix of nuclear, renewables, coal andnatural Cell F3 Composition gas as per EIA projections Carbon Tax on Taxon total emissions from jet fuel and battery charging Cell F4 Emissions($/lb) Grid Electricity Rate Electricity tariff: 1 for Industrial rate,2 for Commercial rate. It is fair to Cell F5 assume that airportcharging would be on the industrial rate. Battery Salvage % of initialbattery cost recaptured in a secondary market Cell H3 Value Battery CostLevel of projection for battery costs, Low through High (L = 1, M = 2,Cell H4 Projection H = 3) Battery Cycle Life Number of flights thebattery supports prior to its secondary market Cell H5 use BatteryConstruction Lbs carbon produced per lb of produced battery Cell J3 TeDPIs the aircraft already a Turbo-electric Distributed Propulsion aircraftCell J4 (Yes = 1, No = 0). This determines whether the mass of electricmachines is already captured in the aircraft OEW mass Core ThermalEfficiency of extracting the energy from jet fuel to provide thrust CellJ5 Efficiency energy Machines & Drives Level of projection for powerdensity of electrical system, Low through Cell L3 Tech Progress High (L= 1, M = 2, H = 3) Motor Rating (MW) Power rating of each electricalmachine in MW Cell L4 per Engine Propulsive Efficiency Aerodynamicefficiency of the airframe Cell L5 Battery Progress Level of projectionfor energy density of batteries, Low through High Cell N3 (L = 1, M = 2,H = 3). Maximum Battery Represents the structural/volumetric limitationof the airframe battery Column N & Mass holding capacity Cell N4 %Weight Reduction If the aircraft is designed to be sold in ether aconventional or hybrid Cell N5 with Optionally Hybrid configuration,this represents the % of removal of hybrid equipment Engine whenoperating in a conventional configuration. If all machines and drives,protection, etc are removed for non-hybrid feasible routes, this wouldbe 100% weight reduction. 0% reduction implies that the motors and powerelectronics, etc, remain in the aircraft. Note: the batteries are notincluded in this parameter, their mass is treated separately.

The scenarios for exercising the aircraft may be created by selection ofthe dependent input variables. The selection of the aircraft and thedependent input variables determines the dependent input variables, suchas those shown in Table 4. These are generated from regressions asdiscussed in the following section:

TABLE 4 Dependent Input Variables Dependent input Excel variablesFunction Description column/cell $/gallon Jet fuel price in $/gallonCell B7 $/KWh Electricity cost for charging the batteries in $/KWh CellD7 Charging CO2 Lb of carbon produced per KWh of electrical energyconsumed in Cell F7 charging the battery Carbon Tax on $/lb ofemissions - assumed the same tax rate is applied to jet fuel Cell H7emissions emissions and emissions from power stations Battery Cost $/KWhof battery installed in the aircraft Cell J7 Total drive power KW/Kg.Average combined power density of power electronics and Cell L7 systemdensity electrical machines Energy Density Battery energy density Wh/KgCell N7 Overall electrical Average combine efficiency of the powerelectronics and electrical Cell P7 drive efficiency machine

Input Assumptions on Annual Projections

The annual projected assumptions used in HIBET are based on publishedindustry forecasts as of 2016/2017. The forecasts are based on threedifferent levels of progression, low, medium and high. Liner andquadratic regressions are used to characterize the forecasts to allow amathematical representation of the trends such that intermediate valuesmay be interpolated for specific cases of interest.

Fuel Costs

Fuel cost projections are based on those published by the EnergyInformation Administration (EAI) in the Annual Energy Outlook2016^(REF). Jet fuel price projections extracted from the Annual EnergyOutlook are shown in Table 5. The regression based reproduction of thisdata is shown in Table 6.

TABLE 5 Jet fuel cost projections (2015 dollars per gallon) Year LowMedium High 2015 1.62 1.62 1.62 2020 1.16 2.18 3.99 2030 1.47 2.87 5.412040 2.15 3.74 6.04

TABLE 6 Regression reproduced jet fuel cost projections (2015 dollarsper gallon) Year Low Medium High 2015 1.62 1.62 1.62 2020 1.18 2.04 3.472025 1.21 2.47 4.67 2030 1.47 2.89 5.38 2035 1.81 3.32 5.74 2040 2.153.74 5.85

Energy Costs

Energy cost projections are based on those published by the EnergyInformation Administration (EAI) in the Annual Energy Outlook 2016REF.Energy price projections extracted from the Annual Energy Outlook areshown in Table 7. The regression based reproduction of this data isshown in Table 8. Charging CO2 Costs

TABLE 7 Energy cost projections (2015 cents per kilowatthours) 2015 20202025 2030 2035 2040 Commercial 10.5 10.7 10.9 11 10.7 10.5 Industrial6.9 7.1 7.3 7.5 7.3 7.2

TABLE 8 Regression reproduced energy cost projections (2015 cents perkilowatthours) 2015 2020 2025 2030 2035 2040 RATE L M H L M H L M H L MH L M H L M H Comm'l 10.4 10.4 10.4 10.5 10.7 10.9 10.7 10.9 11.4 10.711.0 11.8 10.4 10.7 11.6 10.2 10.5 11.4 Industrial 6.9 6.9 6.9 7.0 7.17.3 7.1 7.3 7.6 7.3 7.6 8.2 7.3 7.5 8.2 7.1 7.3 8.0

Charging CO2 Costs

Charging CO2 costs are the product of CO2 emission projections andpredictions of CO2 emission taxation. HIBET assumes grid emissiontaxation is the same cost basis as that applied to aviation emissionsper lb of carbon.

CO2 emission projections are based on a combination of the projectedgrid composition and the projected individual power plant emissions. Theprojected grid composition of is based on the reference case from theEIA 2014 Annual Energy Outlook, Table 9:

TABLE 9 EIA Reference Case Future U.S. Grid Composition; Billions KWhinstalled capacity^(REF) Power Plant 2011 2012 2020 2025 2030 2035 2040Coal 1,733 1,512 1,646 1,689 1,692 1,679 1,675 Petroleum 30 23 18 19 1919 19 Natural Gas 1,014 1,228 1,268 1,401 1,552 1,708 1,839 NuclearPower 790 769 779 779 782 786 811 Renewable 517 502 667 711 748 787 851Sources Other 19 19 24 24 24 24 24 Total 4,103 4,054 4,402 4,622 4,8155,004 5,219

The individual energy source lifecycle emissions for energy productionare based on estimates published by the Intergovernmental Panel onClimate Change (IPCC)REF. These combined with installed capacity, Table9, derives the basis for grid CO2 productions shown in Table 10. Theregression based reproduction of this data is shown in Table 11 in termsof gCO2/KWh and IbCO2/KWh since the latter is used in the model. The %nuclear selected in HIBET reduces the CO2 by the same %.

TABLE 10 Projections gCO2/KWh^(REF) Year Low Medium High 2000 615 510455 2010 600 490 435 2020 550 472 420 2030 545 470 415 2040 540 465 412

TABLE 11 Regression reproduced grid CO2 projections, gCO2/KWh(lbCO2/KWh) Year Low Medium High 2000 615 (1.3558) 535 (1.1795) 455(1.0031) 2010 565 (1.2451) 493 (1.0875) 422 (0.9299) 2020 553 (1.2200)484 (1.0666) 414 (0.9132) 2030 551 (1.2142) 482 (1.0618) 413 (0.9094)2040 550 (1.2129) 481 (1.0607) 412 (0.9086)

Fuel CO2 Emission Taxation

These costs are based on predictions of the taxation schemes beingconsidered by the ICAO on carbon emissions in the aviation industry.ICAO and IATA recognizes the need to address the global challenge ofclimate change and adopted a set of ambitious targets to mitigate CO2emissions from air transport. The aviation industry vision is to achievethe following:

An average improvement in fuel efficiency of 1.5% per year from 2009 to2020;

A cap on net aviation CO2 emissions from 2020 (carbon-neutral growth);and

A reduction in net aviation CO2 emissions of 50% by 2050, relative to2005 levels.

In October 2016 it was agreed that the Carbon Offset and ReductionScheme for International Aviation (CORSAIR) would be introduced forinternational aviation as follows:

Pilot phase (from 2021 through 2023) and first phase (from 2024 through2026) would apply to States that have volunteered to participate in thescheme; and

Second phase (from 2027 through 2035) would apply to all States thathave an individual share of international aviation activities in RTKs inyear 2018 above 0.5 per cent of total RTKs or whose cumulative share inthe list of States from the highest to the lowest amount of RTKs reaches90 per cent of total RTKs, except Least Developed Countries (LDCs),Small Island Developing States (SIDS) and Landlocked DevelopingCountries (LLDCs) unless they volunteer to participate in this phase

Battery Costs

FIG. 7 illustrates an example of projected battery costs. The projectedbattery costs in $/KWh are also shown in Table 12. These projected costswere extracted from the projections published by the Journal of NatureClimate Change. The highest costs are based on the projection of theupper limit of the 95% confidence interval for the whole industry (upperboundary of medium grey region). The lowest costs are based on theprojection of the lower limit of the 95% confidence interval for themarket leaders (lower boundary of light gray region).

TABLE 12 Battery cost $/KWh extracted from Figure Year Low High 2008 6001600 2010 450 1200 2012 325 900 2014 250 670 2015 200 600 2020 175 4502025 150 2030 125 300 2040 125

TABLE 13 Regression reproduced battery cost $/KWh Year Low Medium High2008 603 1139 1675 2010 415 774 1133 2012 321 592 863 2014 265 483 7002015 245 443 641 2020 181 318 456 2025 147 253 360 2030 127 213 300 2040103 167 231

Energy Density

Industry projections anticipate an improvement of 4% per year forLithium-ion batteries. Some estimate that lithium ion technology cangrow up to a theoretical maximum energy density of 850 Wh/Kg.State-of-the-art technology is currently at 200 Wh/Kg which if projectedthrough to 2040 at a 4, 5 or 6% growth rate for low, medium and highprogressions derives the values in Table 14.

TABLE 14 Projected growth in battery energy density (theoreticallycapable with lithium-ion chemistry) Year 4% growth 5% growth 6% growth2017 200 200 200 2020 225 232 238 2025 274 296 319 2030 333 377 427 2035405 481 571 2040 493 614 764

TABLE 15 Additional extrapolation to model sensitivity to advancedbattery chemistries Year Low - 1 Medium - 3 High - 5 2017 200 200 2002020 225 238 252 2025 274 319 370 2030 333 427 544 2035 405 571 799 2040493 764 1174

Total Drive Power Density

Total drive power density is the product of power density of theelectrical machine technology progression and the power electronicstechnology progression. Examples of projections for these technologiesare shown in Tables 16 and 17.

TABLE 16 Projection of power density of electrical machine technologyColumn title Low Medium High 2017 5 5 5 2025 7 9 12 2035 10 13 20 204011 15 24

TABLE 17 Projection of power density of power electronics technologyYear Low Medium High 2017 7.5 7.5 7.5 2025 10 13 20 2035 14 20 25 204016 23 27

Overall Electrical Efficiency

Overall electrical efficiency is the product of efficiency of theelectrical machine technology progression and the power electronicstechnology progression. Example projections for these technologies areshown in Tables 18 and 19.

TABLE 18 Projection of efficiency of electrical machine technology YearLow Medium High 2017 0.97 0.97 0.97 2025 0.975 0.97825 0.9825 2035 0.980.985 0.99 2040 0.9825 0.9875 0.9925

TABLE 19 Projection of efficiency of power electronics technology YearLow Medium High 2017 0.97 0.97 0.97 2025 0.975 0.97825 0.9825 2035 0.980.985 0.99 2040 0.9825 0.9875 0.9925

HIBET Functions

The majority of the columns in HIBET contain functions to calculate theenergy requirements for conventional and hybridized aircraft.

TABLE 20 Functions fora conventional aircraft Excel Function FunctionDescription column/cell Fueled TOW (lb) Total aircraft weight (fuel +oew + payload) Column E Potential energy (MJ) MJ of stored potentialenergy for the lb of fuel; 43.15 MJ/kg; 2.2 lb per Column F kg ThrustWork (MJ) Energy converted to thrust after losses associated with corethermal Column G efficiency and propulsive efficiency

The functions for a hybridized aircraft (per flight) are summarized inTable 21.

TABLE 21 Functions for a hybridized aircraft Excel Function FunctionDescription column/cell % Energy Limit Energy from the motors divided bytotal energy needed. This column Column H selects one of two algorithmsbased on: Pm <= Pcr or Pm > Pcr, where Pm is the motor rating and Pcr isrequired cruise power for the total aircraft weight (fuel + payload +OEW as a ratio of MTOW). Refer to section on % energy limit OptimizedBattery Refer to section on optimized battery works Column I works OEW(lb) Updated OEW to account for electrical motors and displaced fuel (noColumn J battery mass included) Thrust Work (MJ) Updated energy requiredto provide thrust with the added weight of Column K electrical systemcomponents and batteries Energy/Fuel Work Chooses the lowest value ofcolumn H (% energy limit) and column I Column L Ratio (optimized batteryworks) Battery Energy (MJ) Calculates the applied (thrust) energy tocome from the battery: Column M multiplication of column K and column LActual Battery Mass Selects the minimum of column N or column M appliesthe Column O inefficiences to get the actual mass for the actual energycarried, i.e. more than applied energy Stored Battery Based on column O(actual battery mass) and battery energy density Column P Energy (MJ)Stored Fuel Energy Calculates the applied (thrust) energy to come fromthe fuel: column K Column Q (MJ) (thrust work) less the energy in columnP with efficiencies applied Fuel Mass Mass of fuel for the hybridizedaircraft based on column Q (fuel mass) Column R Is a check of column I(Optimized battery works) Column S Energy Mass Summation of battery massand fuel mass Column T Total Mass Total aircraft weight (fuel + oew +payload + battery) Column U MTOW Energy Limit Calculates the factor thatdetermines the optimial split between fuel Column V and battery energybased on Mass constraints and required energy. Refer to section onSolver Range (nm) Range; a repeat of column A Column X

Energy Optimization

In some examples, HIBET leverages two algorithms in order to determinethe optimized energy split. First, HIBET determines the maximum amountof energy that can be provided by the electrical machines over themission range and ratio's this to the total required energy for thatmission. This is referred to as the “% Energy Limit,” (Column H).Second, based on a user request and the constraint of maximum electricalenergy delivery above, HIBET uses the “Optimized Battery Works,” (columnI) to solve for the any one of the following determined by user input(for example by selection of Operating Mode, Cell B4):

-   -   Utilize maximum allowable aircraft weight, MTOW    -   minimum relative cost    -   minimum fuel consumption    -   minimum emissions

% Energy Limit (Column H)

This is the maximum amount of energy that can be provided by theelectrical machines and is dependent on the following parameters:

-   P_(to)—Power required for take-off per engine (Take-off power per    engine multiplied by ratio total mass to fuel mass).-   P_(cr)—Power required for cruise per engine (Cruise power per engine    multiplied by ratio total mass to fuel mass.-   P_(m)—Motor Rating (MW) per engine (with a multiplier to account for    a Turboelectric Distributed Propulsion configuration)-   R_(to)—range for take-off (for example, 100 nm)-   R_(tot)—total range of given flight

The % Energy Limit algorithm accounts for the two conditions, Pm<=Pcrand Pm>Pcr, each of which is derived independently for take-off andcruise flight segments. Descent is not necessarily characterized ortaken into account when determining the % Energy Limit. FIG. 8Aillustrates energy calculation parameters where Pm<=Pcr. FIG. 8Billustrates energy calculation parameters where Pm>Pcr.

Take-Off Flight Segment

Scenario P_(m)<=P_(cr)

FIGS. 9A and 9B illustrates a % Energy Limit calculation for thetake-off flight segment under the condition where Pm<=Pcr and range=100nm, where FIG. 9A illustrates the calculation of Electrical Energy, andFIG. 9B illustrates the calculation of the Total Energy.

When Pm<=Pcr, % Energy Ratio is defined as the shaded area in FIG. 9Adivided by the shaded area in FIG. 9B. Because Rto=Rtot, they cancel andthe ratio of electrical energy to total energy is:

P_(m)/AVERAGE(P_(to),P_(cr))

Scenario P_(m)>P_(cr)

FIGS. 10A and 10B illustrates a % Energy Limit calculation for thetake-off flight segment under the condition where Pm>Pcr and range=100nm, where FIG. 10A illustrates the calculation of Electrical Energy, andFIG. 10B illustrates the calculation of the Total Energy.

When Pm>Pcr, % Energy Ratio is defined as the shaded area in FIG. 10Adivided by the shaded area in FIG. 10B, or ratio of electrical energy tototal energy is:

$ {\frac{{{Area}\mspace{11mu} 1} + {{Area}\mspace{14mu} 2} + {{Area}\mspace{14mu} 3}}{{{Area}\mspace{14mu} 1} + {{Area}\mspace{14mu} 2} + {{Area}\mspace{14mu} 3} + {{Area}\mspace{14mu} 4}}{{Area}\mspace{14mu} 1\text{:}\mspace{14mu} P_{m}*\frac{( {P_{m} - P_{to}} )}{( {P_{cr} - P_{to}} )}R_{to}}{{Area}\mspace{14mu} 2\text{:}\mspace{14mu} \frac{1}{2}*\lbrack {R_{to} - {( \frac{( {P_{m} - P_{to}} )}{( {P_{cr} - P_{to}} )} )R_{to}}} \rbrack*( {P_{m} - P_{cr}} )}{{Area}\mspace{14mu} 3\text{:}\mspace{14mu} P_{cr}*\lbrack {R_{to} - {( \frac{( {P_{m} - P_{to}} )}{( {P_{cr} - P_{to}} )} )R_{to}}} \rbrack}{{Area}\mspace{14mu} 4\text{:}\mspace{14mu} \frac{1}{2}*( \frac{( {P_{m} - P_{to}} )}{( {P_{cr} - P_{to}} )} )R_{to}}} \rbrack*( {P_{to} - P_{m}} )$

Cruise Flight Segment

Scenario Pm<=Pcr

FIGS. 11A and 11B illustrates a % Energy Limit calculation for thecruise flight segment under the condition where Pm<=Pcr and range=100nm, where FIG. 11A illustrates the calculation of Electrical Energy, andFIG. 11B illustrates the calculation of the Total Energy.

If Pm<=Pcr, % Energy Ratio is defined as the shaded area in FIG. 11Adivided by the shaded area in FIG. 11B, or the ratio of electricalenergy to total energy is

(P_(m)*R_(to))+(P_(m)*(R_(tot)−R_(to))/AVERAGE((P_(to),P_(cr))*R_(to))+(P_(cr)*(R_(tot)−R_(to)))

Scenario Pm>Pcr

FIGS. 12A and 12B illustrates a % Energy Limit calculation for thecruise flight segment under the condition where Pm>Pcr and range=100 nm,where FIG. 12A illustrates the calculation of Electrical Energy, andFIG. 12B illustrates the calculation of the Total Energy.

If Pm>Pcr, % Energy Ratio is determined as the shaded area in FIG. 12Adivided by the shaded area in FIG. 12B, or ratio of electrical energy tototal energy is:

$ {\frac{{{Area}\mspace{11mu} 1} + {{Area}\mspace{14mu} 2} + {{Area}\mspace{14mu} 3} + {{Area}\mspace{14mu} 5}}{{{Area}\mspace{14mu} 1} + {{Area}\mspace{14mu} 2} + {{Area}\mspace{14mu} 3} + {{Area}\mspace{14mu} 4} + {{Area}\mspace{14mu} 5}}{{Area}\mspace{14mu} 1\text{:}\mspace{14mu} P_{m}*\frac{( {P_{m} - P_{to}} )}{( {P_{cr} - P_{to}} )}R_{to}}{{Area}\mspace{14mu} 2\text{:}\mspace{14mu} \frac{1}{2}*\lbrack {R_{to} - {( \frac{( {P_{m} - P_{to}} )}{( {P_{cr} - P_{to}} )} )R_{to}}} \rbrack*( {P_{m} - P_{cr}} )}{{Area}\mspace{14mu} 3\text{:}\mspace{14mu} P_{cr}*\lbrack {R_{to} - {( \frac{( {P_{m} - P_{to}} )}{( {P_{cr} - P_{to}} )} )R_{to}}} \rbrack}{{Area}\mspace{14mu} 4\text{:}\mspace{14mu} \frac{1}{2}*( \frac{( {P_{m} - P_{to}} )}{( {P_{cr} - P_{to}} )} )R_{to}}} \rbrack*( {P_{to} - P_{m}} )$Area  5:  P_(m) * (R_(tot) − R_(to))

Optimized Battery Works (or Solver) (Column I)

Based on user selection, HIBET optimizes the energy split between jetfuel and battery energy to achieve one of the following:

-   minimum MTOW—option 1-   minimum relative cost—option 2-   minimum fuel consumption—option 3-   minimum emissions—option 4

Each of the optimizations identified above rely on a factor k, whichrepresents the maximum fraction of energy that to be provide by thebattery, which is calculated in Column V.

The parameters used to derive factor k are listed below. The parametersconcern the conventional aircraft, the hybridized aircraft operatedconventionally (i.e. weight of electrical system, such as machines anddrives, but not battery), and the hybridized aircraft utilizing a mix ofjet fuel and battery energy.

-   M_(f)—Mass of fuel—Column R-   M_(b)—Mass of battery—Column O-   M_(pay)—Mass of payload—Column D-   M_(eow)—Mass of hybridized aircraft (unfueled, no batteries, no    payload)—Column J-   MTOW—Maximum Take-Off Weight—Cell T7-   M_(FTOW)—Mass of flight ready conventional aircraft—Column E-   M_(c)—Mass of flight ready conventionally operated aircraft, i.e.    includes the weight of the electrical system but no batteries—may or    may not be calculated by HIBET-   M_(h)—Mass of flight ready hybrid aircraft—Column U-   M_(MD)—Mass of electrical components (machines and drives)-   TW_(FTOW)—Thrust Work for conventional aircraft—Column G-   TW_(c)—Thrust Work (conventionally operated hybrid aircraft, i.e.    includes the weight of the electrical system but no batteries)—Value    may or may not be outputted by HIBET-   TW_(h)—Thrust Work (hybrid)—Column K-   E_(b)—Energy stored in battery—Column Q-   E_(f)—Energy stored in fuel—Column P-   TW_(b)—Thrust Work from battery—same a Column M-   TW_(f)—Thrust Work from fuel—Value may or may not be outputted by    HIBET-   η_(t)—gas turbine core thermal efficiency—Cell J5-   η_(p)—airframe propulsive efficiency—Cell L5-   η_(e)—overall electrical system efficiency—Cell P7-   ρ_(f)—specific energy density of fuel-   ρ_(p)—specific energy density of batteries

For the special case that the energy split is optimized to utilize theaircraft rated MTOW the total mass for a hybrid aircraft is defined as:

MTOW=M_(oew)+M_(pay)+M_(f)+M_(b)

Therefore:

MTOW−M_(oew)−M_(pay)=M_(f)+M_(b)

Representing mass in terms of the Stored Energy, E:

${{MTOW} - M_{oew} - M_{pay}} = {\frac{E_{f}}{\rho_{f}} + \frac{E_{b}}{\rho_{b}}}$

Denoting the energy in terms of Thrust Work, TW:

${{MTOW} - M_{oew} - M_{pay}} = {\frac{TW_{f}}{\eta_{t}\eta_{p}\rho_{f}} + \frac{TW_{b}}{\eta_{e}\eta_{p}\rho_{b}}}$

If the total applied Thrust Work (battery and jet fuel combined) isrepresented by TW_(h):

TW_(h)=TW_(f)+TW_(b)=(1−k)TW_(h)+kTW_(h)

Then:

${{MTOW} - M_{oew} - M_{pay}} = {{\frac{1}{\eta_{t}\eta_{p}\rho_{f}}( {1 - k} ){TW}_{h}} + {\frac{1}{\eta_{e}\eta_{p}\rho_{b}}{kTW}_{h}}}$${{MTOW} - M_{oew} - M_{pay}} = {{{kTW}_{h}\lbrack {\frac{1}{\eta_{t}\eta_{p}\rho_{f}} - \frac{1}{\eta_{e}\eta_{p}\rho_{b}}} \rbrack} + {\frac{1}{\eta_{t}\eta_{p}\rho_{f}}{TW}_{h}}}$$\frac{{MTOW} - M_{oew} - M_{pay}}{{TW}_{h}} = {{k\lbrack {\frac{1}{\eta_{t}\eta_{p}\rho_{f}} - \frac{1}{\eta_{e}\eta_{p}\rho_{b}}} \rbrack} + \frac{1}{\eta_{t}\eta_{p}\rho_{f}}}$${\frac{{MTOW} - M_{oew} - M_{pay}}{{TW}_{h}} - \frac{1}{\eta_{t}\eta_{p}\rho_{f}}} = {k\lbrack {\frac{1}{\eta_{t}\eta_{p}\rho_{f}} - \frac{1}{\eta_{e}\eta_{p}\rho_{b}}} \rbrack}$$\frac{\frac{{MTOW} - M_{oew} - M_{pay}}{{TW}_{h}} - \frac{1}{\eta_{t}\eta_{p}\rho_{f}}}{\lbrack {\frac{1}{\eta_{t}\eta_{p}\rho_{f}} - \frac{1}{\eta_{e}\eta_{p}\rho_{b}}} \rbrack} = k$

Also:

$\frac{{Thrust}\mspace{14mu} {work}\mspace{14mu} {hybrid}_{{Col}.K}}{\begin{matrix}{{Thrust}\mspace{14mu} {work}\mspace{14mu} {hybridized}\mspace{14mu} {operating}} \\{conventionally}\end{matrix}} = \frac{{Hybrid}\mspace{14mu} {mass}_{{Col}.U}}{{Mass}\mspace{14mu} {hybridized}\mspace{14mu} {operating}\mspace{14mu} {{conv}.}}$

This can be written as:

$\frac{TW_{h}}{TW_{c}} = \frac{M_{h}}{M_{c}}$

Where

M_(c)=Fueled Takeoff Weight_(col.E)+Electrical system weight

M_(c)=M_(FTOW)+M_(MD)

So:

${\frac{TW_{h}}{TW_{c}} = \frac{M_{h}}{M_{FTOW} + M_{MD}}}{{TW_{h}} = {\frac{M_{h}}{M_{FTOW} + M_{MD}} \times TW_{c}}}$

Then:

$\frac{\frac{( {{MTOW} - M_{oew} - M_{pay}} )}{\frac{M_{h} \times {TC}_{c}}{M_{FTOW} + M_{MD}}} - \frac{1}{\eta_{t}\eta_{p}\rho_{f}}}{\lbrack {\frac{1}{\eta_{t}\eta_{p}\rho_{f}} - \frac{1}{\eta_{e}\eta_{p}\rho_{b}}} \rbrack} = k$$\frac{{\frac{M_{FTOW} + M_{MD}}{{TW}_{c}} \times \frac{( {{MTOW} - M_{oew} - M_{pay}} )}{M_{h}}} - \frac{1}{\eta_{t}\eta_{p}\rho_{f}}}{\lbrack {\frac{1}{\eta_{t}\eta_{p}\rho_{f}} - \frac{1}{\eta_{e}\eta_{p}\rho_{b}}} \rbrack} = k$

The ratio of mass between the hybridized aircraft operatedconventionally and the conventional aircraft will be equivalent to theratio between the Thrust Work for the two aircraft, hence:

$\frac{TW_{c}}{TW_{FTOW}} = \frac{M_{c}}{M_{FTOW}}$

So:

${TW_{c}} = {\frac{M_{c}}{M_{FTOW}} \times TW_{FTOW}}$

Since M_(c) is the mass of the hybrid aircraft operated conventional, orput differently, the conventional aircraft the weight of the hybridizedelectrical system components, then:

${TW_{c}} = {\frac{( {M_{FTOW} + M_{MD}} )}{M_{FTOW}} \times {TW}_{FTOW}}$

Therefore k is defined by:

$\frac{\begin{matrix}{\frac{M_{FTOW} + M_{MD}}{{TW}_{FTOW} \times {( {M_{FTOW} + M_{MD}} )/M_{FTOW}}} \times} \\{\frac{( {{MTOW} - ( {M_{oew} + M_{MD}} ) - M_{pay}} )}{MTOW} - \frac{1}{\eta_{t}\eta_{p}\rho_{f}}}\end{matrix}}{\lbrack {\frac{1}{\eta_{t}\eta_{p}\rho_{f}} - \frac{1}{\eta_{e}\eta_{p}\rho_{b}}} \rbrack} = k$

Maximize Battery Usage Based on MTOW Limit

This solver calculates the optimum energy to be provided by the batteryregardless of emissions and cost. The intent is to displace as muchfuel, or utilize as much battery capacity, as possible while maintainingsufficient overall energy mix to complete the mission range within theMTOW limit. Other limiting factors, such as the maximum zero fuel weight(MZFW) or volumetric constraints for battery storage, are achievedthrough user selection of the maximum allowable battery weight, which isa parameter in the solver. In terms of FIG. 4 that shows the HIBETlimits, this solver allows the value limit to be exceeded, whereas thepower limit and the structural/volumetric limit are user defined by themotor power rating and maximum allowable battery weight.

This is achieved by Column I selecting the lowest value between the cellin Column H and the corresponding cell in Column V, where Column H isthe % Energy Limit and Column V is the factor of energy to be providedby the battery.

MIN(H11,V11)

Minimum Relative Cost

This solver follows the MTOW limit until it becomes more expensive forthe aircraft to utilize batteries, i.e. in terms of FIG. 4, the point atwhich the bottom plot crosses over the x-axis. At this point HIBETreverts to a conventional aircraft for further increase in range.

This is achieved by Column I comparing total hybrid energy cost, ColumnAJ to total conventional aircraft cost, Column AB. When hybridizationcosts exceed convention then the delta costs are set to zero and theconventional aircraft is selected.

IF(AJ11<=AB11,MIN(H11,V11),0

Minimum Fuel Consumption

This solver follows the MTOW limit until the hybridized aircraftutilizes more jet fuel than the conventional due to the increased energydemand required to carry the additional mass of the batteries. I.e. theadditional energy requirement is no longer compensated by the availablestored battery energy.

This is achieved by Column I comparing the jet fuel emissions of thehybridized aircraft, Column AD, to the emissions of the conventionalaircraft, Column Y. When the jet fuel emissions from the hybridizedaircraft exceed those of the conventional, then the solver reverts to aconventional aircraft.

IF(AD11>Y11,0,MIN(H11,V11))

Minimum Emissions

This solver follows the MTOW limit until the hybridized aircraftproduces more emissions than the conventional; one example is thebattery charging source producing more emissions than the burning of jetfuel.

This is achieved by Column I comparing the total emissions (jet fuel andbattery charging) of the hybridized aircraft, Column AF, to theemissions of the conventional aircraft, Column Y. When the totalemissions for the hybridized aircraft exceed those of the conventional,then the solver reverts to a conventional aircraft.

IF(AF11>Y11,0,MIN(H11,V11)),0)))

Aircraft Usage Distributions

HIBET is able to reference a lookup table of typical aircraftutilizations across flight ranges and numbers of passengers. Forairframes for which such data exists, this enables the benefit ofhybridization to be averaged across the whole fleet usage, in otherwords, short to long range flights. FIG. 13A shows an exampledistribution of range and number of passengers for an Airbus A320family. FIG. 13B shows an example distribution of range and number ofpassengers for a Boeing B737 family.

Demonstration of Constraints on Hybridization

As described earlier in connection with FIG. 4, there are constraintsthat determine the feasibility of hybridization for a given airframesizing. For a particular airframe, HIBET may perform a simulation inwhich HIBET follows the constraint curve shown in FIG. 4, namelyinitially along the power limit, then along the battery mass limit, andthen along the MTOW limit until reaching the value limit. This may bereferred to as “hitting the constraints.” By following the constraintcurve (hitting the constraints), HIBET may determine correspondingenergy/fuel work ratios, battery masses, relative costs, and relativeemissions for an airframe. FIG. 14A illustrates a graph generated byHIBET displaying the corresponding battery masses and energy/fuel workratios. FIG. 14B illustrates a graph generated by HIBET displaying thecorresponding relative costs and relative emissions.

HIBET may determine an effect of a change of one or more characteristicsof the airframe or other variables on the energy/fuel work ratios, thebattery masses, the relative costs, and the relative emissions for anairframe. FIGS. 15A and 15B illustrate the effect of doubling the motorpower ratings per engine. FIG. 15A illustrates the energy/fuel workratios and the battery masses generated by the HIBET given a first powerrating of the motor. FIG. 15B illustrates the energy/fuel work ratiosand the battery masses generated by HIBET given a second power rating ofthe motor, where the second power rating is double the first powerrating.

As another example, FIGS. 16A and 16B illustrate the effects ofincreasing an aspect of the structure/volumertic limit of the aircraftevaluated in HIBET. In particular, FIG. 16A illustrates the energy/fuelwork ratios and the battery masses generated by the HIBET given a firstallowable battery mass. FIG. 16B illustrates the energy/fuel work ratiosand the battery masses generated by HIBET given a second allowablebattery mass, where the second allowable battery mass is 25% larger thanthe first allowable battery mass.

In still another example, FIGS. 17A and 17B illustrate the effects ofincreasing the MTOW of the aircraft as evaluated by HIBET. Inparticular, FIG. 17A illustrates the energy/fuel work ratios and thebattery masses generated by the HIBET given a first MTOW. FIG. 17Billustrates the energy/fuel work ratios and the battery masses generatedby HIBET given a second MTOW, where the second MTOW is 3% larger thanthe first MTOW.

In yet another example, FIGS. 18A and 18B illustrate the effects ofchanging the value limit constraint as evaluated by HIBET. The valuelimit constraint changes the range at which hybrid propulsion loses itsbenefit and is no longer feasible. For example changing the battery costprojection from a low to a high value and reducing the battery salvagevalue from 50% to 0 may result in lowering the value limit constraint.FIG. 18A illustrates the energy/fuel work ratios and the battery massesgenerated by the HIBET before changing the battery cost projections andbattery salvage value. FIG. 18B illustrates the energy/fuel work ratiosand the battery masses generated by HIBET after changing the batterycost projections and battery salvage value.

Listing of HIBET Functions and Variables

Examples of independent input functions are summarized in Table A-1

TABLE A-1 Independent Input Variables Independent input Excel variablesFunction Description column/cell Projected Year Year selected for allregression based projection functions/formulas Cell B3 Operating ModeSelection of solving parameter. 1 = Solves for maximum displacement CellB4 of the fuel using battery regardless of cost and emissions whilingachieving mission range, 2 = Solves for minimum cost of energy, 3 =Solves for minimum jet fuel consumption, 4 = Solves for minimum totalemissions Grid Energy Cost Level of projection for energy costs, Lowthrough High (L = 1, M = 2, Cell B5 Outlook H = 3) Fuel Cost ProjectionLevel of projection for jet fuel costs, Low through High (L = 1, M = 2,Cell D3 H = 3) Nuclear Discount The discount rate, otherwise referred toas “discounted cash flow Cell D4 Rate analysis” is the effectivereduction in future projected profits when accounting for them intoday's monetary value. Nuclear is significantly more sensitive todiscount rate than coal or gas due to being capital intensive. Thediscount rate chosen to cost a nuclear power plant's capital over itslifetime is arguably the most sensitive parameter to overall costs andhence levelized cost of electricity (LOCE). At a 3% discount ratenuclear power is typically the cheapest form of energy production. At 7%it is comparable to coal, but still cheaper than gas. At 10% it iscomparable to both. % Nuclear % of dedicated carbon free energyproduction for charging batteries, Cell D5 Generation i.e. 40% nuclearwould imply 60% is still based on regional grid mix composition RegionalUS Grid Represents the US grid mix of nuclear, renewables, coal andnatural Cell F3 Composition gas as per EIA projections Carbon Tax on Taxon total emissions from jet fuel and battery charging Cell F4 Emissions($/lb) Grid Electricity Rate Electricity tariff: 1 for Industrial rate,2 for Commercial rate. It is fair to Cell F5 assume that airportcharging would be on the industrial rate. Battery Salvage % of initialbattery cost recaptured in a secondary market Cell H3 Value Battery CostLevel of projection for battery costs, Low through High (L = 1, M = 2,Cell H4 Projection H = 3) Battery Cycle Life Number of flights thebattery supports prior to its secondary market Cell H5 use BatteryConstruction Lbs carbon produced per lb of produced battery Cell J3 TeDPIs the aircraft already a Turbo-electric Distributed Propulsion aircraftCell J4 (Yes = 1, No = 0). This determines whether the mass of electricmachines is already captured in the aircraft OEW mass Core ThermalEfficiency of extracting the energy from jet fuel to provide thrust CellJ5 Efficiency energy Machines & Drives Level of projection for powerdensity of electrical system, Low through Cell L3 Tech Progress High (L= 1, M = 2, H = 3) Motor Rating (MW) Power rating of each electricalmachine in MW Cell L4 per Engine Propulsive Efficiency Aerodynamicefficiency of the airframe Cell L5 Battery Progress Level of projectionfor energy density of batteries, Low through High Cell N3 (L = 1, M = 2,H = 3). Maximum Battery Represents the structural/volumetric limitationof the airframe battery Column N & Mass holding capacity Cell N4 %Weight Reduction If the aircraft is designed to be sold in ether aconventional or hybrid Cell N5 with Optionally Hybrid configuration,this represents the % of removal of hybrid equipment Engine whenoperating in a conventional configuration. If all machines and drives,protection, etc are removed for non-hybrid feasible routes, this wouldbe 100% weight reduction. 0% reduction implies that the motors and powerelectronics, etc, remain in the aircraft. Note: the batteries are notincluded in this parameter, their mass is treated separately.

Examples of dependent input functions are summarized in Table A-2

TABLE A-2 Dependent Input Variables Dependent input Excel variablesFunction Descripnon column/cell $/gallon Jet fuel price in $/gallon CellB7 $/KWh Electricity cost for charging the batteries in $/KWh Cell D7Charging CO2 Lb of carbon produced per KWh of electrical energy consumedin Cell F7 charging the battery Carbon Tax on $/lb of emissions -assumed the same tax rate is applied to jet fuel Cell H7 emissionsemissions and emissions from power stations Battery Cost $/KWh ofbattery installed in the aircraft Cell J7 Total drive power KW/Kg.Average combined power density of power electronics and Cell L7 systemdensity electrical machines Energy Density Battery energy density Wh/KgCell N7 Overall electrical Average combine efficiency of the powerelectronics and electrical Cell P7 drive efficiency machine

Example airframe input variables are described in Table A-3.

TABLE A-3 Airframe Input Variables Independent input Excel variablesFunction Description column/cell Payload/Max Payload Ratio of actualpayload to maximum allowable payload Cell P3 Takeoff Power per MW ratingof take-off power per engine Cell P4 Engine Cruise Power per MW ratingcruise power per engine Cell P5 Engine Max Payload Max allowable payloadCell R7 MTOW Maximum Take-Off Weight Cell T7 Range (nm) Flight range insegments of 100 nm Column A Fuel (lb) Fuel required for conventionalairframe for a given nm - fuel Column B consumption derived from theaircraft model (APD and Mission software) converted to a regressionbased formula for range, max payload and MTOW OEW (lb) Operating EmptyWeight;, or Basic Operating Weight for the Column C conventionalaircraft; the weight of the conventional aircraft, unfueled with nopayload Payload (lb) Selected payload for the simulation - product ofthe maximum Column D payload (Cell R7 and the ratio of Payload to MaxPayload (Cell P3). Represents the weight of passengers and their baggage

Example functions for a conventional aircraft (per flight) are describedin Table A-4.

TABLE A-4 Functions for a conventional aircraft Excel Function FunctionDescription column/cell Fueled TOW (lb) Total aircraft weight (fuel +oew + payload) Column E Potential energy (MJ) MJ of stored potentialenergy for the lb of fuel; 43.15 MJ/kg; 2.2 lb per Column F kg ThrustWork (MJ) Energy converted to thrust after losses associated with corethermal Column G efficiency and propulsive efficiency

Example functions for a hybridized aircraft (per flight) are describedin Table A-5.

TABLE A-5 Functions for a hybridized aircraft Excel Function FunctionDescription column/cell % Energy Limit Energy from the motors divided bytotal energy needed. This column Column H selects one of two algorithmsbased on: Pm <= Pcr or Pm > Pcr, where Pm is the motor rating and Pcr isrequired cruise power for the total aircraft weight (fuel + payload +OEW as a ratio of MTOW). Refer to section on % energy limit OptimizedBattery Refer to section on optimized battery works Column I works OEW(lb) Updated OEW to account for electrical motors and displaced fuel (noColumn J battery mass included) Thrust Work (MJ) Updated energy requiredto provide thrust with the added weight of Column K electrical systemcomponents and batteries Energy/Fuel Work Chooses the lowest value ofcolumn H (% energy limit) and column I Column L Ratio (optimized batteryworks) Battery Energy (MJ) Calculates the applied (thrust) energy tocome from the battery: Column M multiplication of column K and column LActual Battery Mass Selects the minimum of column N or column M appliesthe Column O inefficiences to get the actual mass for the actual energycarried, i.e. more than applied energy Stored Battery Based on column O(actual battery mass) and battery energy density Column P Energy (MJ)Stored Fuel Energy Calculates the applied (thrust) energy to come fromthe fuel: column K Column Q (MJ) (thrust work) less the energy in columnP with efficiencies applied Fuel Mass Mass of fuel for the hybridizedaircraft based on column Q (fuel mass) Column R Is a check of column I(Optimized battery works) Column S Energy Mass Summation of battery massand fuel mass Column T Total Mass Total aircraft weight (fuel + oew +payload + battery) Column U MTOW Energy Limit Calculates the factor thatdetermines the optimial split between fuel Column V and battery energybased on Mass constraints and required energy. Refer to section onSolver Range (nm) Range; a repeat of column A Column X

Example costs for conventional aircraft (per flight) are described inTable A-6

TABLE A-6 Cost variable data for a conventional aircraft Excel Costingvariables Function Description column/cell Baseline emissions Calculatesthe mass of carbon emitted by jet fuel as used in engine. Column Y (lb)For energy lb of fuel there is 3.1 lb of carbon emission. Fuel Cost ($)Column B (fuel mass) multiplied by cost rate Column Z Carbon Tax ($)column Y (baseline emissions) multiplied by carbon tax on emissionsColumn AA ($/lb) Baseline Cost ($) Column Z (fuel cost) added to columnAA (carbon tax) Column AB

Example costs for hybridized aircraft (per flight) are described inTable A-7

TABLE A-7 Cost variable data for a hybridized aircraft Excel Costingvariables Function Description column/cell Emissions fuel (lb)Calculates the mass of carbon emitted by jet fuel as used in Column ADhybridized engine. For energy lb of fuel there is 3.1 lb of carbonemission. Emissions Calculates the emissions produced in charging thebattery and in Column AE Battery/Energy (lb) construction of the batteryTotal Emissions (lb) Addition of the fuel and battery emissions ColumnAF Cost Fuel ($) Column R (fuel mass) multiplied by cost rate Column AGCost Battery/Energy Addition of the cost of charging the battery and thecost of purchasing Column AH ($) the battery Carbon Tax ($) Column AF(total emissions) multiplied by carbon tax on emissions Column AI ($/lb)Total energy Cost ($) Addition of cost of fuel (column AG), cost ofbattery & its Column AJ energy(column AH) and the cost of carbon tax(column AI)

Examples of hybridized outputs are provided in Table A-8.

TABLE A-8 Output data for a conventional aircraft Excel Output variablesFunction Description column/cell Relative Cost (%) Difference betweenhybrid and conventional total energy costs ratioed Column AL to theconventional. Negative value represents a reduction in cost compared tothe conventional Relative emissions Difference between hybrid andconventional emissions ratioed to the Column AM (%) conventional.Negative value represents a reduction in cost compared to theconventional Relative on-board Difference between hybrid andconventional jet fuel emissions ratioed Column AN emissions (%) to theconventional. Negative value represents a reduction in jet fuel basedemissions compared to the conventional Fleet usage Uses a lookupfunction to extract weightings on the usage distribution Column APdistribution of an aircraft for each of the ranges. This applies theweightings for aircraft mission usage against each 100 nm range. Referto aircraft usage distribution. Fleet usage Column AQ distribution

Examples of single payload results are provided in Table A-9.

TABLE A-9 Single payload results data for a hybridized aircraft ExcelResults Function Description column/cell Average energy cost Weightedbaseline cost (columns AB*AQ) less the weighted total Cell S3 delta forsingle payload energy cost (columns AJ*AQ) Delta in fuel cost perWeighted conventional fuel cost (columns Z*AQ) less the weighted Cell S4flight for single payload hybrid fuel cost(columns AG*AQ) Delta inenergy cost per Weighted Cost Battery/Energy (columns AH*AQ) Cell S5flight for single payload Max battery range for Looks up the maximum“stored battery energy” (column P) and Cell U3 single payload returnsthe corresponding “range” (column X) Max battery mass for Looks up themaximum “battery mass” (column O) and returns its Cell U4 single payloadvalue Fleet average emissions Weighted baseline emissions (columns Y*AQ)less the weighted Cell U5 delta for single payload total hybridemissions (columns AF*AQ)

Details of Mathematical Functions

Conventional Aircraft:

Column A: Range (nm)

Column B: Fuel (lb)

=(0.00000004*(MaxPayload_(Cell.R7)*Payload_(Cell,P3)/MaxPayload_(Cell.R7))−0.0007)*Range_(Col.A){circumflexover( )}2+(−0.00002*(MaxPayload_(Cell.R7)*Payload_(Cell.P3)/MaxPayload_(Cell.R7))+8.0997)*Range_(Col.A)+(0.0076*(MaxPayload_(Cell.R7)*Payload_(Cell.P3)/MaxPayload_(Cell.R7))+2265.1)

Column C: OEW (lb)

Constant

Column D: Payload (lb)

Constant

Column E: Fueled Take-Off Weight (lb)

=Fuel mass_(col.B)+OEW_(Col.C)+Payload mass_(Col.D)

Column F: Potential Energy (MJ)

=Fuel mass_(col.B)×(43.15/2.2)

Column G: Thrust Work (MJ)

=Potential Energy_(col.F)×η_(t) _(cell.j5) ×η_(p) _(cell.L5)

Energy Analysis

Column H: % Energy Limit

Refer to section

Column I: Optimized Battery Works %

Refer to section

Hybridized Aircraft

${{Column}\mspace{14mu} J\text{:}\mspace{14mu} {OEW}\mspace{14mu} ({lb})} = {{OEW}_{{col}.C} + {2 \times {( \frac{2.2 \times P_{m}}{1000} )/{total}}\mspace{14mu} {drive}\mspace{14mu} {system}\mspace{14mu} {power}\mspace{14mu} {density}}}$

(NOTE: If TeDP, then for the case that hybrid not feasible, hybridweight reduction per Cell N5)

${{Column}\mspace{14mu} K\text{:}\mspace{11mu} {Thrust}\mspace{14mu} {Work}\mspace{14mu} ({MJ})} = {{Thrust}\mspace{14mu} {Work}_{{col}.G} \times \frac{{Total}\mspace{14mu} {Mass}_{{Col}.U}}{{Fueled}\mspace{14mu} {TOW}_{{Col}.E}}}$

Column L: Energy/Fuel Work Ratio

=Minimum of % Energy Limit_(Col.H) and Optimized Battery Works_(Col.I)

Column M: Battery Energy (MJ)

=Energy/Fuel Work Ratio_(Col.L)×Thrust Work_(col.K)

Column N: Max Battery Mass (lb)

Defined by Cell N4

Column O: Actual Battery Mass (lb)

Minimum of Max Battery Mass_(Col.N) and actual required battery mass:

${\frac{{Battery}\mspace{14mu} {Energy}_{{Col}.M}}{\eta_{e_{{Cell},{P\; 7}}} \times \eta_{p_{{{Cell}.L}\; 5}}} \div {Battery}}\mspace{14mu} {energy}\mspace{14mu} {{density}_{{{Cell}.N}\; 7}/( \frac{277.778}{2,2} )}$${{Column}\mspace{14mu} P\text{:}\mspace{14mu} {Stored}\mspace{14mu} {Battery}\mspace{14mu} {Energy}\mspace{14mu} ({MJ})} = {{Actual}\mspace{14mu} {battery}\mspace{14mu} {mass}_{{Col}.O} \times {Battery}\mspace{14mu} {energy}\mspace{14mu} {{density}_{{{Cell}.N}\; 7}/( \frac{277.778}{2.2} )}}$${{Column}\mspace{14mu} Q\text{:}\mspace{14mu} {Stored}\mspace{14mu} {Fuel}\mspace{14mu} {Energy}\mspace{14mu} ({MJ})} = {{{Thrust}\mspace{14mu} {Work}_{{Col}.K}} - ( \frac{{Stored}\mspace{14mu} {battery}\mspace{14mu} {energy}_{{Col}.P} \times \eta_{e_{{{Cell}.P}\; 7}} \times \eta_{p_{{{Cell}.L}\; 5}}}{\eta_{t_{{{Cell}.J}\; 5}} \times \eta_{p_{{{Cell}.L}\; 5}}} )}$Column  R:  Fuel  Mass  (lb) = 2.2 × Stored  Fuel  Energy_(Col.Q)/43.15

Column S: This is check to insure the electrical and fuel energy ratiois as suggested by the optimized battery works; i.e. a check againstColumn I:

$\frac{\begin{matrix}{{Stored}\mspace{14mu} {battery}\mspace{14mu} {energy}_{{Col}.P} \times} \\{{Overall}\mspace{14mu} {electrical}\mspace{14mu} {erive}\mspace{14mu} {efficiency}_{{{Cell}.P}\; 7}}\end{matrix}}{\begin{matrix}{( {{Stored}\mspace{14mu} {Battery}\mspace{14mu} {energy}_{{Col}.P} \times {Overall}\mspace{14mu} {electrical}\mspace{14mu} {erive}\mspace{14mu} {efficiency}_{{{Cell}.P}\; 7}} ) +} \\( {{Stored}\mspace{14mu} {fuel}\mspace{14mu} {energy}_{{Col}.Q} \times {Core}\mspace{14mu} {thermal}\mspace{14mu} {efficiency}_{{{Cell}.J}\; 5}} )\end{matrix}}$

Column T: Energy Mass (lb)

=Fuel mass_(Col.R)+Battery mass_(Col.O)

Column U: Total Mass (lb)

=Battery mass_(Col.O)+Fuel mass_(Col.R)+OEW_(Col.J)+Payload_(Col.D)

Column V: MTOW Energy Limit

Refer to section

Baseline Operating Costs (Conventional Aircraft)

Column Y: Baseline Emissions (lb)

=Fuel_(Col.B)×3.1

Column Z: Fuel Cost ($)

=Fuel_(Col.B)×6.79

Column AA: Carbon Tax ($)

=Baseline emissions_(Col.Y)×Carbon tax on emissions_(Cell.H7)

Column AB: Baseline Cost ($)

=Fuel cost_(Col.Z)+Carbon Tax_(Col.AA)

Hybrid Operating Costs

  Column  AD:  Emissions  Fuel  (lb) = Fuel  mass_(Col.R) × 3.1${{Column}\mspace{14mu} {AE}\text{:}\mspace{14mu} {Emissions}\mspace{14mu} {{Battery}/{Energy}}\mspace{14mu} ({lb})} = {\frac{\begin{matrix}{{ChargingCO}\; 2_{{{Cell}.F}\; 7} \times} \\{{Stored}\mspace{14mu} {battery}\mspace{14mu} {energy}_{{Col}.P} \times 277.778}\end{matrix}}{1000} + \frac{{Battery}\mspace{14mu} {construction}\mspace{14mu} {carbon}_{{{Cell}.J}\; 3}}{{Battery}\mspace{14mu} {life}\mspace{14mu} {cycle}_{{{Cell}.H}\; 5} \times {Battery}\mspace{14mu} {mass}_{{Col}.O}}}$Column  AF:  Total  Emissions  (lb) = Emissionsfuel_(Col.AD) + Emissions  battery/energy_(Col.AE)  Column  AG:  Cost  Fuel  ($)  Fuel  mass_(Col.R) × $/gallon_(Cell.B 7)/6.79${{Column}\mspace{14mu} {AH}\text{:}\mspace{14mu} {Cost}\mspace{14mu} {{Battery}/{Energy}}\mspace{14mu} (\$)} = {{{Stored}\mspace{14mu} {battery}\mspace{14mu} {energy}_{{Col}.P} \times {\$/{KWh}_{{{Cell}.D}\; 7}} \times ( \frac{277.778}{1000} )} + ( {\frac{{Battery}\mspace{20mu} {mass}_{{Col}.O}}{{Battery}\mspace{14mu} {cycle}\mspace{14mu} {life}_{{Cell}.{HS}}} \times \frac{{Battery}\mspace{14mu} {costs}_{{{Cell}.J}\; 7} \times {energy}\mspace{14mu} {density}_{{{Cell}.\; N}\; 7}}{1000 \times 2.2}} )}$Column  AI:  Carbon  Tax  ($) = Total  emissions_(Col.AF) × Carbon  tax  emissions_(Cell.H 7)Column  AJ:  Total  Energy  Cost  ($) = Cost  fuel_(Col.AG) + Cost  battery  energy_(Col.AH) + Carbon  tax_(Col.AI)

Outputs

Column  AL:  Relative  Cost  (%)$\frac{{{Total}\mspace{14mu} {energy}\mspace{14mu} {cost}_{{Col}.{AJ}}} - {{Baseline}\mspace{14mu} {cost}_{{Col}.{AB}}}}{{Baseline}\mspace{14mu} {cost}_{{Col}.{AB}}}$Column  AM:  Relative  Emissions  ($)$\frac{{{Total}\mspace{14mu} {emissions}_{{Col}.{AF}}} - {{Baseline}\mspace{14mu} {emissions}_{{Col}.Y}}}{{Baseline}\mspace{14mu} {emissions}_{{Col}.Y}}$Column  AN:  Relative  On-Board  Emissions$\frac{{{Emissions}\mspace{14mu} {fuel}_{{Col}.{AD}}} - {{Baseline}\mspace{14mu} {emissions}_{{Col}.Y}}}{{Baseline}\mspace{14mu} {emissions}_{{Col}.Y}}$

EXAMPLE FLEET ANALYSIS

As mentioned above, HIBET is able to reference a lookup table of typicalaircraft utilizations across flight ranges and numbers of passengers.This enables an analysis of the benefit of hybridization across a wholefleet of one type of aircraft.

A first input received by the HIBET may be information about theaircraft under investigation. FIG. 19 is an example of a graphical userinterface generated by HIBET through which aircraft data may be entered.An operator may define characteristics of the aircraft underinvestigation in, for example, the left two columns. A couple of optionsin the left column relate to assumptions made in the calculation aboutthe added weight that a hybrid system adds to the baseline aircraftweight. For example, pax payload, MTOW, operating empty weight (OEW), %weight reduction with optionally hybrid aircraft, and maximum batterymass. In the center cells of the graphical user interface, theaircraft's operating sequence is defined, with a power defined for eachstage of flight along with either a time and/or a range defined. Thecruise range may be a variable for which the tool calculates a series ofvalues for, which will be shown below.

A second input of the HIBET may be a fuel mass map for the aircraft. Asshown in FIG. 20, the fuel mass map may include a table of cells, whereeach cell of the table indicates a fuel mass required for acorresponding payload and corresponding mission range. Shown in FIG. 20,is performance data obtained from the aircraft manufacturer, operators,an engine manufacturer, and/or other source. Here, the required fuelmass is reduced to a function of two variables: the range of the flightand its payload weight. Accordingly, the fuel mass map may be table thatincludes cells, where each cell includes a fuel mass (for a conventionalaircraft) required to complete a flight, and the rows and columns areflight ranges and payload weight, respectively. The fuel mass may beused by the HIBET to provide an estimate of energy required for thegiven platform for a given flight mission.

A third input of the HIBET may be a table that includes a distributionof mission profiles (payloads and ranges) that the aircraft underinvestigation made over a time period. This data may be used by the toolto extrapolate an estimated energy-usage benefit across the entireoperating fleet of the type of aircraft under investigation. FIG. 21illustrates an example table of mission distributions for the aircraft,where each cell in the table indicates the frequency that the aircraftmade a flight of a corresponding payload and a corresponding range. Forexample, each cell may include the number of times any of the aircraftsin the fleet flew a mission with that combination of payload and rangedivided by the total number of missions flown by the aircraft in thefleet.

With the characteristics of the aircraft under investigationsufficiently provided, the tool may collect information about eithercurrent or hypothetical economic and technological factors that mayaffect the cost of energy (fuel or electric), cost of components, and/orweight of the aircraft in an estimated hybrid-electric configuration.FIG. 22 illustrates an example of a graphical user interface to receiveeconomic and technological variables pertaining to energy and hybridcomponent cost.

FIG. 23 illustrates an example of a graphical user interface configuredto receive additional technological factors and general characteristicsof a conventional turbine engine that the hybrid system will be comparedagainst. In this example, the HIBET incorporates projections for each ofthe economic and technological factors that go into factoring the energycost of conventional and hybrid electric propulsion systems. Theprojections are then used to create formulae that accept a projectionyear and a “level of progress” from, for example, 1-3. This allows theuser to quickly and easily run batches of hypothetical scenarios, whichhelps generate an understanding of which factors heavily influence theenergy cost benefit of hybrid-electric systems.

FIG. 24 shows an example of a graphical user interface configured toreceive details of the aircraft hybrid-electric system from a user. Asan example, user inputs may be received in the two lightest coloredinput fields 2402 and 2404 relating to a “subfleet” definition. Inparticular, a subfleet max payload 2402 and a subfleet max range 2404may be entered. Hybrid-electric propulsion generally benefitsshorter-range flights the quickest. To capture the benefit that thehybrid system brings to the short-range flights while not punishing thesystem for being more inefficient on longer-haul flights, the “subfleet”option was created which sets a cap on the range of a mission that thehybrid system would be calculated to perform. This is equivalent of theHIBET assuming that a short-range hybrid option may be operated indense, short-haul markets, such as the Eastern US, while the longer-haulflights may be serviced instead by aircraft with conventional turbinevariants. The content of the two lightest colored input fields 2402 and2404 may be copied information from the aircraft inputs shown in FIG.19.

FIG. 25 illustrates an example of a graphical user interface showing atable of economic and technological variables that pertain to energy andhybrid system component costs. Varying the year and the various inputfactors affect the output variables in this table, which are thenutilized in the upcoming energy and cost calculations.

FIG. 26 illustrates an example graphical user interface displayingenergy requirement calculations of the aircraft. For example, FIG. 26depicts the initial energy requirement calculations of the user-definedaircraft using the airframe and mission definition, and fuel mass, fromFIGS. 1 and 2. The energy in fuel is then converted to thrust work usingthe conventional turbine performance inputs from FIGS. 5 and 6.

Once the amount of energy has been calculated for each range increment,the tool uses the economic and technological factors shown in FIG. 25 toconvert that into an energy cost for the conventional turbine engineaircraft, in terms of, for example, fuel cost, emissions, and taxes onthose emissions. FIG. 27 illustrates an example of a graphical userinterface displaying energy cost calculation of conventionalturbine-powered aircraft based on the output table of economic andtechnological variables.

With the required energy and associated cost of the conventionallypowered aircraft determined, the tool then calculates the correspondingvalues for the hybrid-electric system. The first step is depicted inFIG. 28. FIG. 28 illustrates a graphical user interface displaying therequired energy calculation during each stage of the mission for ahybrid-electric aircraft. Examples of mission stages include a taxistage, a climb stage, a cruise stage, and a descent stage. For eachrange interval, the mission of the specified hybrid aircraft is brokenup into the stages taxi out, climb, cruise, descent and taxi in. Theamount of energy required for each stage is calculated then totaled inthe right-most column.

Then, similarly to the required energy calculation, the energy availablefrom the electric powertrain for each stage is derived from theaircraft, economic, and technological input parameters. This maximumavailable hybridization energy (in other words, available from theelectric powertrain) is depicted in FIG. 29. FIG. 29 illustrates anexample of a graphical user interface displaying maximum energy duringeach stage of the mission for a hybrid-electric aircraft.

The available energy from the hybrid system is then divided by the totalenergy needed (for each range increment) to arrive at the maximumpercentage of energy that the defined hybrid system may source for thedefined flight profile in the defined economic conditions with thedefined technological conditions. The result of the division is shown inthe column labeled “% Energy Limit” of FIG. 30. FIG. 30 illustrates anexample of a graphical user interface displaying this “% Energy Limit”,which is related to the power limit. The power limit may be a percentageof total energy required and averaged over the entire flight mission.The hybrid system is then analyzed by first adding to the amount ofthrust work the hybrid aircraft based on the increased weight of thesystem and the increased drag needed to cool the components (anadjustable setting in FIG. 24). The battery/fuel work ratio is chosen asthe minimum of the optimized battery works percentage and the % energylimit.

The optimized battery limit is an interesting lever because, in oneexample, the optimized battery limit is, for any particular range, theminimum of the % Energy Limit (a variation of the power limit) or theMaximum-Take-Off-Weight (MTOW) limit (shown in FIG. 31). Alternatively,by changing the operating mode (in other words, the optimization mode),the HIBET may determine the optimized battery limit as, for anyparticular range, the minimum of the % Energy Limit and: the lowest-costenergy mixture, the energy mixture resulting in the lowest fuelemissions, or even total emissions (including the carbon released ingenerating the electricity stored in the batteries).

Once the percentage of battery (in other words, the optimized batterylimit) is determined, the HIBET may calculate the battery weight andenergy based on the economic and technological inputs. The remainingenergy needed comes from fuel, so the required fuel energy and weight isobtained therefrom. This section of the calculation may be recursive,because the amount of battery energy to install on the aircraft dependson the thrust work required, which depends on the weight of theaircraft, which depends on the amount of battery in the aircraft. TheHIBET is designed in a way which allows this calculation to occurrapidly. FIG. 30 illustrates an example of a graphical user interfacethat displays an indication 3002 of the amount of battery to install ondefined hybrid-electric aircraft for each interval of a mission range.The indication 3002 of the amount of battery to install includes abattery mass in this example.

FIG. 31 shows the last three columns of the calculations described inthe previous paragraph about FIG. 30. In particular, FIG. 31 shows thetotal energy and mass defined for the hybrid-electric aircraft and theMTOW Limit that is described above.

FIG. 32 illustrates an example of a graphical user interface displayingthe emissions and the costs associated with the conventional gas-turbineversion of the aircraft under investigation from the fuel quantity shownin FIG. 26 and from the economic inputs. Each of the depicted emissionsand costs corresponds to a respective mission range.

FIG. 33 illustrates an example of a graphical user interface displayingthe emissions and the costs associated with the hybrid-electric versionof the aircraft from the fuel quantity in FIG. 30 and the economicinputs. The battery energy emissions may be calculated from user-inputon the percentage of renewable energy powering the electrical grid. Inthe right-most columns, the cost and emissions of the hybrid system arecompared directly with the conventional gas-turbine.

With the individual flight costs and emissions determined for eachmission range of the defined aircraft and economic conditions, the toolcan utilize the fleet data (from FIG. 21) to estimate the benefit of anentire fleet of hybrid-electric aircraft. The size of the measuredbenefit can range in scope from a subset of a single operator to theentirety of the specified aircraft globally, and is entirelyuser-defined.

To accomplish this calculation, the distribution of flights at theuser-defined payload is selected and normalized. FIG. 34 illustrates anexample of a graphical user interface displaying a table for normalizingthe distribution of flights of the defined airframe with the definedpayload. Then the fuel-usage of the conventionally-powered aircraftversion is compared to the hybrid-powered version of the aircraft,calculated as described above. Some columns contain zeros where numbersmight be expected. The max hybrid flight range is user-defined in thetable shown in FIG. 24, as “SubFleet Max Range”. This allows the user todefine a maximum range of hybrid-electric flight missions underinvestigation, which is currently the most efficient (and costeffective) way for an operator to plan flights. It is one way to helpprevent the tool from penalizing the hybrid architecture for theless-efficient longer flights versus the more-efficient shorter flights.

The product of the conventionally-powered energy cost for each missionrange and usage distribution and subtracted from the hybridized cost toarrive at a cost savings on an average per-flight basis. The same isalso performed for the emissions.

FIG. 35 illustrates an example of a graphical user interface displayingaverage per-flight fuel cost and emissions savings of the definedaircraft and payload. The HIBET in some examples may extrapolate theaverage per-flight cost and emissions to a user-defined fleet size inthe table shown in FIG. 36. FIG. 36 illustrates an example of agraphical user interface displaying fleet-averaged results of aircrafthybridization.

In some examples, the user may set the size of the fleet underinvestigation to arrive at the total fleet-wide cost effect ofimplementing hybrid-electric propulsion systems on the targetedaircraft. FIG. 37 illustrates an example of a graphical user interfacedisplaying the total annual fleet-wide savings due to hybridizing thefleet.

As mentioned above, HIBET may be implemented in software. FIG. 38illustrates an example of a computing device 3802 or system thatincludes HIBET 3812. Examples of the computing device 3802 include adesktop computer, a laptop computer, a server machine, a blade server, amobile device, a tablet device, a mobile phone, an internet of things(IoT) device, an embedded system, or any other apparatus configured toexecute software.

The computing device 3802 or system shown in FIG. 38 includes aprocessor 3804, a display device 3806, an input device 3808, and amemory 3810. HIBET 3812 is included in the memory 3810. HIBET 3812includes constants 3814, input parameters 3816, programmatic functions3818, and a graphical user interface 3822. Examples of the constants3814, the input parameters 3816, and the programmatic functions 3818 aredescribed above. One example of the programmatic functions 3818described herein includes an optimized battery works module 3820. Theoptimized battery works module is configured to perform the optimizedbattery works programmatic function described in detail above.

The memory 3810 may be any device for storing and retrieving data or anycombination thereof. The memory 3810 may include non-volatile and/orvolatile memory, such as a random access memory (RAM), a read-onlymemory (ROM), an erasable programmable read-only memory (EPROM), orflash memory. Alternatively or in addition, the memory 3810 may includean optical, magnetic (hard-drive) or any other form of data storagedevice.

The processor 3804 may be any device that performs logic operations. Theprocessor 3804 may be in communication with the memory 3810. Theprocessor 3804 may also be in communication with additional components,such as the display device 3806 and the input device 3808. The processor3804 may include a general processor, a central processing unit, aserver device, an application specific integrated circuit (ASIC), adigital signal processor, a field programmable gate array (FPGA), adigital circuit, an analog circuit, a controller, a microcontroller, anyother type of processor, or any combination thereof. The processor 3804may include one or more elements operable to execute computer executableinstructions or computer code embodied in the memory 3810 or in othermemory.

The display device 3806 may be any electro-optical device for displayingdata. Examples of the display device 3806 may include a liquid crystaldisplay (LCD), an organic light-emitting diode (OLED), a cathode raytube (CRT), an electro-luminescent display, a plasma display panel(PDP), a vacuum florescent display (VFD), a touch screen or any othertype of display device. The display device 3806 may be integral to thecomputing device 3802 or a discrete component separate from thecomputing device 3802. Examples of the input device 3808 include akeyboard, a mouse, a keypad, a stylus, a touch screen, and/or any otherdevice configured to receive human input.

The graphical user interface (GUI) 3822 is a type of user interfacewhich facilitates human interaction with electronic devices, such ascomputers, hand-held devices, mobile devices, household appliances andoffice equipment. The GUI 3822 may offer graphical icons, and visualindicators as opposed to text-based interfaces, typed command labels ortext navigation to fully represent the information and actions availableto a user. The actions may be performed through direct manipulation ofthe graphical elements. The GUI 382 may include software, hardware, or acombination thereof through which people interact with a machine,device, computer program or any combination thereof. Examples of the GUI3822 may include a web page, a rendered display page, or any other datastructure describing how a display screen or a portion of a displayscreen is to be displayed. The GUI 3822 is depicted as being included inHIBET 3812. Alternatively, the GUI 3822 may be generated by a differentcomponent, such as a spreadsheet application, in response toprogrammatic functions 3818 included in HIBET 3812.

Each component may include additional, different, or fewer componentsthan depicted. For example, the programmatic functions 3818 may includemany modules in addition to the optimized battery works 3820.

FIG. 39 illustrates a flow diagram of an example of steps performed byHIBET 3812. The steps may include additional, different, or feweroperations than illustrated in FIG. 39. The steps may be executed in adifferent order than illustrated in FIG. 39.

Operations may begin by receiving (3902), prior to a flight by a hybridelectric aircraft, an indication of a limitation of battery mass for thehybrid electric aircraft.

Operations may continue by determining (3904), based on the indicationof the limitation of battery mass and prior to the flight, an amount ofelectrical energy and determining (3906) an amount of jet fuel necessaryfor the hybrid electric aircraft to complete the flight based on anoptimization of an energy split between the electrical energy and thejet fuel.

Operations may complete by causing (3908) an indication of the amount ofelectrical energy and/or the amount of jet fuel to be displayed in thegraphical user interface 3822 and/or to be otherwise outputted. Forexample, the indication of the amount of electrical energy may beoutputted as an audio signal.

The computing device 3802 or system may be implemented in many differentways. Each module, such as the optimized battery works module 3820, maybe hardware or a combination of hardware and software. For example, eachmodule may include an application specific integrated circuit (ASIC), aField Programmable Gate Array (FPGA), a circuit, a digital logiccircuit, an analog circuit, a combination of discrete circuits, gates,or any other type of hardware or combination thereof. Alternatively orin addition, each module may include memory hardware, such as a portionof the memory 3810, for example, that comprises instructions executablewith the processor 3804 or other processor to implement one or more ofthe features of the module. When any one of the modules includes theportion of the memory that comprises instructions executable with theprocessor, the module may or may not include the processor. In someexamples, each module may just be the portion of the memory 3810 orother physical memory that comprises instructions executable with theprocessor 3804 or other processor to implement the features of thecorresponding module without the module including any other hardware.Because each module includes at least some hardware even when theincluded hardware comprises software, each module may be interchangeablyreferred to as a hardware module.

Some features are shown stored in a computer readable storage medium(for example, as logic implemented as computer executable instructionsor as data structures in memory). All or part of the system and itslogic and data structures may be stored on, distributed across, or readfrom one or more types of computer readable storage media. Examples ofthe computer readable storage medium may include a hard disk, a floppydisk, a CD-ROM, a flash drive, a cache, volatile memory, non-volatilememory, RAM, flash memory, or any other type of computer readablestorage medium or storage media. The computer readable storage mediummay include any type of non-transitory computer readable medium, such asa CD-ROM, a volatile memory, a non-volatile memory, ROM, RAM, or anyother suitable storage device. However, the computer readable storagemedium is not a transitory transmission medium for propagating signals.

The processing capability of the system may be distributed amongmultiple entities, such as among multiple processors and memories,optionally including multiple distributed processing systems.Parameters, databases, and other data structures may be separatelystored and managed, may be incorporated into a single memory ordatabase, may be logically and physically organized in many differentways, and may implemented with different types of data structures suchas linked lists, hash tables, or implicit storage mechanisms. Logic,such as programs or circuitry, may be combined or split among multipleprograms, distributed across several memories and processors, and may beimplemented in a library, such as a shared library (for example, adynamic link library (DLL)).

To clarify the use of and to hereby provide notice to the public, thephrases “at least one of <A>, <B>, . . . and <N>” or “at least one of<A>, <B>, <N>, or combinations thereof” or “<A>, <B>, . . . and/or <N>”are defined by the Applicant in the broadest sense, superseding anyother implied definitions hereinbefore or hereinafter unless expresslyasserted by the Applicant to the contrary, to mean one or more elementsselected from the group comprising A, B, . . . and N. In other words,the phrases mean any combination of one or more of the elements A, B, .. . or N including any one element alone or the one element incombination with one or more of the other elements which may alsoinclude, in combination, additional elements not listed. Unlessotherwise indicated or the context suggests otherwise, as used herein,“a” or “an” means “at least one” or “one or more.”

While various embodiments have been described, it will be apparent tothose of ordinary skill in the art that many more embodiments andimplementations are possible. Accordingly, the embodiments describedherein are examples, not the only possible embodiments andimplementations.

What is claimed is:
 1. A non-transitory computer readable storage mediumcomprising a plurality of computer executable instructions, the computerexecutable instructions executable by a processor, the computerexecutable instructions comprising: instructions executable to receive,prior to a flight by a hybrid electric aircraft, an indication of alimitation of battery mass for the hybrid electric aircraft;instructions executable to determine, based on the indication of thelimitation of battery mass and prior to the flight, an amount ofelectrical energy and an amount of jet fuel necessary for the hybridelectric aircraft to complete the flight based on an optimization of anenergy split between the electrical energy and the jet fuel; andinstructions executable to cause an indication of the amount ofelectrical energy and the amount of jet fuel to be displayed in agraphical user interface and/or to be otherwise outputted.
 2. Thecomputer readable storage medium of claim 1, wherein the optimization ofthe energy split includes maximizing a battery usage based on the hybridelectric aircraft initially having a Maximum Take-Off Weight (MTOW),while maintaining a sufficient overall energy mix in order to completethe flight.
 3. The computer readable storage medium of claim 2, whereinthe optimization includes maximizing the battery usage regardless of acost of the battery usage relative to jet fuel usage and regardless ofemissions.
 4. The computer readable storage medium of claim 2, whereinthe optimization includes maximizing the battery usage yet minimizingrelative cost by preventing a cost of the battery usage by the hybridelectric aircraft with a battery from exceeding a cost of jet fuel usageby the hybrid electric aircraft without the battery.
 5. The computerreadable storage medium of claim 2, wherein the optimization includesmaximizing the battery usage yet minimizing fuel consumption bypreventing a burn of more fuel by the hybrid electric aircraft with abattery than the hybrid electric aircraft without the battery due to anincreased energy demand caused by the weight of the battery.
 6. Thecomputer readable storage medium of claim 2, wherein the optimizationincludes maximizing the battery usage yet minimizing emissions bypreventing emissions generated by the hybrid electric aircraft carryinga battery from exceeding emissions generated by the hybrid electricaircraft not carrying the battery because of an increased energy demandcaused by the weight of the battery.
 7. The computer readable storagemedium of claim 1, wherein the indication of the amount of electricalenergy and the amount of jet fuel indicates a battery size and/or anumber of batteries to install in the hybrid electric aircraft.
 8. Thecomputer readable storage medium of claim 1, wherein the indication ofthe amount of electrical energy and the amount of jet fuel includes aratio of fuel to electric energy storage.
 9. The computer readablestorage medium of claim 1, wherein the computer executable instructionsthat are executable by the processor are included in a spreadsheet filestored on the computer readable storage medium.
 10. A method comprising:determining an amount of electrical energy and an amount of jet fuelnecessary for a hybrid electric aircraft to complete a flight based on arange of the flight, a payload of the hybrid electric aircraft, anindication of a battery mass limitation of the hybrid electric aircraft,and an optimization of an energy split between the electrical energy andthe jet fuel; and causing an indication of the amount of electricalenergy to be displayed in a graphical user interface and/or to beotherwise outputted.
 11. The method of claim 10, wherein the indicationof the amount of electrical energy comprises battery sizing information.12. The method of claim 10 further comprising determining a ratio offuel to electric energy storage based on characteristics of thehybrid-electric aircraft and economic factors including fuel cost,electricity cost, and carbon taxes.
 13. The method of claim 10 furthercomprising determining, based on fleet-wide usage data of a conventionalaircraft, to determine a value that an introduction of a hybrid-electricpropulsion system would bring to an entire fleet of the conventionalaircraft.
 14. The method of claim 13 wherein the value includes anestimation of economic benefit based on user-specified economicconditions.
 14. The method of claim 13 wherein the value includes fleetaverage energy costs.
 15. The method of claim 13 wherein the valueincludes fleet average emissions reduction.
 16. The method of claim 10further comprising determining and displaying a delta energy cost perflight resulting from use of the hybrid-electric aircraft over acomparable conventional aircraft for the flight.
 17. The method of claim10 further comprising determining and displaying a delta emissions deltaper flight resulting from use of the hybrid-electric aircraft over acomparable conventional aircraft for the flight.
 18. The method of claim10 wherein determining the amount of electrical energy and the amount ofjet fuel necessary for the hybrid electric aircraft to complete theflight is based on estimates of future values for economic factorsincluding future cost of fuel.
 19. The method of claim 10 whereindetermining the amount of electrical energy and the amount of jet fuelnecessary for the hybrid electric aircraft to complete the flight isbased on estimates of future values for technology including futureweight of battery per unit of applied electrical energy.
 20. A systemcomprising: an optimized battery works module configured to determine anamount of electrical energy and an amount of jet fuel necessary for ahybrid electric aircraft to complete a flight based on a range of theflight, a payload of the hybrid electric aircraft, an indication of abattery mass limitation of the hybrid electric aircraft, and anoptimization of an energy split between the electrical energy and thejet fuel; and a graphical user interface comprising the amount ofelectrical energy to be displayed.